This invention concerns filters and more particularly filters used to remove contaminating particles from cutting fluids used in metal working machining.
Large volumes of contaminated cutting liquids are generated in the machining of metal in large scale metal cutting operations such as in the manufacture of engine components in the automotive industry. These liquids are filtered to remove solid particles such as grit, metal chips, etc. in a recirculating system, which returns the filtered liquid for reuse with the machine. The volumes of liquids required for large machining installations has led to the use of indexing belt filters circulated through large tanks.
See U.S. Pat. No. 5,601,729 for an example of such filtering apparatus.
These filters allow great volumes of liquid to be filtered, but do not totally eliminate the presence of stray particles which can get around the edges of the belts, pass through tears in the belt, or otherwise get into the filtered liquid.
Even one metal chip can cause plugging of a coolant nozzle for a machine tool, creating rapid tool failure and possible shut down of the entire installation.
There is thus a need for a failsafe auxiliary filter for removing residual particles from the filtered liquid.
A particular problem associated with cutting fluids in particular is the build up of gelatinous material which has a great tendency to rapidly plug up fine filter openings, such that it is not practical to use fine screen filters to eliminate these stray particles. Also, such apparatus is often operated continuously with automatic controls, and any auxiliary filters used desirably should not require constant maintenance.
It is the object of the present invention to provide a filter and process for filtering out residual particles from filtered cutting fluids recirculated from a machining operation.